Radio reception means



E5111'? 1?, 1947. c STREBE 5- AL 2,422,374

I RADIO RECEPil'IQN MEANS Filed Feb. 16, 1943 2 Sheets-Sheet l 70 AVC CIRCUIT FRANK 6. 57-1955: 6 WILLIAM L. COM Y/vs HA mm, K/EcH, F as TERQHA me/s F01? THE FIRM ATToR/w: v.5.

June 17, 1947.

' Filed Feb. 1a, 1943 F. c. STREBE ET AL 2,422,374

RADIO RECEPTION MEANS 2 Sheets-Sheet 2 lNVENTORS FRANK CST/e555 6 WILLl/JM 1.. COM v/vs HE FIRM ATTOENE vs.

Patented June 17, 1947 UNITED STATES PATENT OFFICE RADIO RECEPTION MEANS Frank C. Strebe and William L. Comyns, Los Angeles, Calif.

Application February 16, 1943, Serial No. 476,114

6 Claims. 1

Our invention relates to radio receivers and is directed particularly to a radio receiver designed to minimize interference with desired signals.

The general object of our invention is to provide a means and method for greatly reducing, if not entirely eliminating, extraneous aperiodic waves in radio reception with little or no resultant reduction of the desired signal wave. It is a further object of our invention to provide means to reduce or preclude static that is both relatively simple and relatively inexpensive. In some practices of our invention one of our purposes is to provide such static-eliminating means that may be readily incorporated in existing conventional receivers.

The objects and advantages of our invention will be readily apparent in the following description, taken with the accompanying drawing.

In the drawing, which is to be considered as illustrative only:

Fig. 1 is a wiring diagram illustrating one practice of our invention in which two vacuum tubes are used;

Figs. 2 and 3 illustrate modifications of the wiring diagram of Fig. 1; and

Fig. 4 is a wiring diagram illustrating a second practice. of our invention involving the use of only one tube.

In Fig. 1 the antenna circuit has two grounded coils in parallel, namely, a first coil H! for Coupling to a first tuning circuit II and a second coil l2 for coupling to a second tuning circuit I3. The resonant frequency of the first circuit may be controlled by the usual tuning condenser l5, and in like manner the second'tuning circuit l3 may be controlled by a tuning condenser l6.

Our invention is based on the concept of tuning one of these circuits for optimum reception of a given signal, detuning the other circuit slightly with respect to the frequency of such signal to reduce by a substantial amount the signal voltage in the'circuit, interrelating the two circuits in a voltage-opposing relation, and transferring the resulting net voltage to the next stage in the receiver. In putting this conception into practice, it is found that the two circuits may be so tuned relative to each other and relative to a given signal that aperiodic waves affect both circuits with substantially equal or comparable voltages while the desired amplitude-modulated signal wave produces substantial signal voltages in the tuned circuit but little or no signal voltages in the detuned circuit whereby the signal voltage is substantially eliminated in the detuned circuit.

Since the two circuits are in voltage-Opposing relation to each other, it may be readily understood that the interference voltages are substantially cancelled, whereas relatively little cancellation of the signal voltage occurs. The net result, then, is the considerable reduction of the instant interference voltage relative to the instant signal voltage delivered by the joint tuning circuits.

The two variable condensers l5 and It may be the sole means for varying the resonant frequencies of the two circuits H and I3, and these two variable condensers may be operable independently, In the preferred practice of our invention, however, we insert what may be termed a padding condenser .or a trimming condenser in at least one of the two circuits to be relied upon primarily for tuning difierentiation, and we further prefer to interconnect the two tuning condensers l5 and I6 for joint manipulation. In the particular arrangement illustrated by Fig. 1, We place a padding condenser l'l in the first tuning circuit II and likewiseplacea similar padding condenser H3 in the second tuning circuit I3. At least one of the two padding condensers I! and I8 may be manually adjustable by the usual screw arrangement.

For the purpose of interrelating the two tuning circuits II and 3 and for connecting them in voltage-opposing relation, we connect the first receiving circuit to a grid 20 in a first vacuum tube 2| and connect the second tuning circuit l3 to a grid 22 in a second vacuum tube 23.

In the preferred practice of our invention involving the use of two such vacuum tubes, we employ a resistance coupling in relating the two tubes to each other. Thus, Fig. 1 shows the plates of the tubes 2| and 23 interconnected by two resistances 25 and 26 in series. A screen grid 21 in the tube 2| and a screen grid 28 in the tube 23 are connected to each other and to one end of a resistance 30. The other end of the resistance 30 is connected to the resistances 25 and 2B at the juncture of these resistances and is also connected to one end of a resistance 3| leading to the positive side of the B voltage supply. The two resistances 25 and 26 place equal voltages on'the plates of the two tubes while the resistances 3i) and 3| regulate the plate and screen Voltages.

The new voltages from the two tuning circuits are transferred to the next stage through a balancing network having the following elements: a condenser 32 connected to the plate of the tube 2|, a condenser 33 connected to the plate of the tube 23, a voltage divider 35, a resistance 36 connecting the condenser 32 to the voltage divider, and a resistance 31 connecting the condenser 33 to the voltage divider. Fig. 1 shows the adjustable contact of the voltage divider connected through a condenser 38 to the grid 40 in the next succeeding stage of the receiver. After proper balance is attained subsequent adjustment is unnecessary and the contact of the voltage divider may be permanently set, If desired, automatic volume control may be connected into the circuit as indicated by the wire 4| without impeding operation in any manner.

In the described balancing network, the two condensers 32 and 33 out 01f direct current and the voltage divider 35 serves the dual function," first, of providing adjustable means for ioalancing the arrangement, and, second, of providing means for taking off uncancelled voltages for transfer -t'o the next stage in the receiver.

In practice, the first circuit ll may be tuned sharply to ,a "desired :signal and the second circult l3 tuned away from the signal sufiicientl'y to obtain the desired result. The proper relatidns'hip between the two circuits maybe quickly found by trial and 'error even by an operator who .has :had no opportunity to practice with the invention.

One feature of the described arrangement is that only one antenna :is employed, instead of two antennas required zfor some systems of static elimination heretofore proposed. Another featurevis that various types of tubes may be :used

successfully, including trlo'des and tetrodes, .as well aspentodes. Another feature :is that ifxthe invention is embodied in .a unit-separate .fromithe receiver, -the tube normally zusediasxthe first F. tubecan be 'dispensedwith and the output of the unit ted into th .grid of the :mixer stage. -01 course, with respect to .a designed unit, the Silencer takes the :place of the first R. Estage.

Figs.:2 and 3 are largely identical with 1, correspondin numerals being employed to indicate corresponding parts. The purpose of these two-insures is to indicate how the :cirerfitarrange mentor Fig. 1 may abe modified zb employing impedance coupling instead of resistance coupling :forinterrelating the .two tubesi l and 22:3.

JInLFig. 2 thep1atesa0f thentubes .2l and 23; are connected by two variable condensers 50-and 251 placed in series, and the grid %52 of. the next stage isoonnected between :the two condensers. The plate of the tube I21l is directly connectedrto the positive :side iof'ithe B voltage supply sthrough anesistancerfiii, aandrthe :plate. of the :tube 23 is likewise so connected through .a resistance *55. The-:screen-grids i121 22B. of the .two "tubes :aire connected together and also connected :toone end of. airesistance :56 leading to 'the positive .side. of theflB voltage supply. The variable condensers 5i] andfirl senveias adjustable meanslforzbalancing the: two :sides of the general circuit for-the :desiredaeffect.

In the arrangement illustrated by 53,, the plates of the two -tubes2l -and 23 are interconnectedhy arprimary coil sll which .:is connected lay-1a :cente'rcap to aresista-ncezfiwl leading vlto the positive side of the B--vo1tage-supply. A see ondarryicoil v'i2,.the center turn ofxwhidh zis:gr 11n ed, is inductively coupled to the primahy coil fifl and maybe connected by wires 63 zand fit to zt-he posts of :the usual nixed input impedance for tra nsterence or the uncancelled voltagge to the next stage. @hescreen grids zliand zd-areinterw connected and are also -'connected to a resistance 66 leading to the positive side of the B voltage supply.

In the second form of our invention represented by Fig. 4, two tuning circuits 10 and H are both connected to the control grid 12 of a vacuum tube 13 in such manner that the two circuits aifect the control grid with voltages of opposite phase in response to antenna voltages. Various circuit arrangements may be employed to achieve thedesi'red 189 shift in voltage. In the present arrangement, for example, the antenna circuit has two oppositely wound primary coils l5 and it coupled respectively to the tuning circuits I0 and H so that an impulse of current in the antenna circuit creates positive voltage in one of the tuning-circuits and negative voltage in the other tuning circuit. The plate circuit of the tube 13 includes the primary side of a coupling transformer ll for transferring the uncancelled signal voltage to the next stage.

The particular circuits chosen to illustrate our invention and to disclose the principles involved will su ggestto those --skilled in the art various changes and-- substitutions under our basic concept, land we reserve the right to all such ,departures from our description that lie :within the sc pe of our appended claims.

llfewclaim as our invention: g

'1 Aradio receiver having: a first vacuum tube having a grid; 2. second vacuum tube haying a grid; at firstareceiving circuit connected to the grid "01f saidefirst tube; a second receiving circuit connected-to the grid 10f said sec nd tube, said two receiving circuits receiving the Lsamesigna-l voltage and the same signal-interferencevoltage, said two circuits being tuned to 1suzfli eiiently idliierent frequencies tozat least-substantially reduce in ;.one"circuit :the #voitageci the signal ,to' which thekother circuit is tuned without precluding substantially equal signal-interference voltages in abet-h .of said circuits; impedance means capacitively connected to the plate circuits of said two tubes to cause mutual voltage cancelslationt-between thetwo tuhes,;..and rout-put means coupled with said two plate Zcircuits :to receive therefrom uncanoel-ledyoltages.

:2. in combinationinva radio receiver: :a pair of input circuits connected to receive ithecsaine signal voltage and the same 1signal=interierence voltageibu't difierentially tuned so :that 10116 input circuit: is tuned to the :signa'l'an'd-the other is deeizlined sufficiently to substantially .ei'iniinate the signej1..=voltage'itherein.withoutjlalrgely reduc ing the :signal interierence yoltaqg eeoonnnon to the zt'woicircuits; zelectron stubemeans comprising two anodes, :and v:two control grids for respec tivel'y ooiitrcl lingrelectronrflow .to .saidcanodes, sa d ggri'ds :bsin'g respectiiiely connected to: :said inputicircints; means for'isupplying substantially identical anode potentials to .said anodes; land means giorzopposing the voltageoutputs of 'gsa'id anodesiandifor-zcreatinglanouiirlllt'fiig alistlbfiia tially sires signal-interference vol a es. :said means includin a vo age-dividin outp t ,rci

sistance-means providing'end terminals and-an" intermediate terminal If or taking "@fi the-output de-tuned sufiiciently to substantially eliminate the signal voltage therein without largely reducing the signal-interference voltage common to the two circuits; electron tube means comprising two anodes, and two control grids for respectively controlling electron flow to said anodes, said grids being respectively connected to said input circuits; impedance means connected between said anodes and providing an intermediate connection substantially electrically centered with respect to said anodes and adapted for connection to a source of anode potential to supply substantially equal potentials to said anodes; a voltage-dividing output resistance means providing end terminals and an intermediate output terminal; and a pair of condensers respectively connecting said anodes to said end terminals to insure the exclusive presence of alternating currents in said output resistance means.

4. In combination: electron tube means comprising two anodes, and two control grids for respectively controlling electron flow to said anodes; a pair of tuned input circuits respective-- ly connected to said control grids; means for changing the tuning of one input circuit with respect to the other; impedance means connected between said anodes and providing an intermediate connection substantially electrically centered with respect to said anodes and adapted for connection to a source of anode potential to supply substantially equal potentials to said anodes; a voltage-dividing output resistance means providing end terminals and an intermediate output terminal; and means for connecting said end terminals of said output resistance means respectively to said anodes.

5. In combination in a radio receiver: a split antenna circuit providing two branches connected in parallel with each other; a pair of input circuits respectively coupled with said branches of said antenna circuit to receive the same signal voltage and the same signal-interference voltage but difierentially tuned so that one input circuit is tuned to the signal and the other is de-tuned sufficiently to substantially eliminate the signal voltage therein without largely reducing the signal-interference voltage common to the two input circuits; first and second screen-grid vacuum tubes providing two anodes, two screen grids, and two control grids; means for respectively connecting said control grids to said input circuits; means for interconnecting said screen grids; and means interconnecting said anodes for opposing the potentials of said anodes to substantially cancel said signal-interference voltage and provide an output voltage varying with the signal voltage.

6. In combination in a radio receiver: a pair of input circuits connected to receive the same signal voltage and the same signal-interference voltage but differentially tuned so that one input circuit is tuned to the signal and the other is de-tuned sufiiciently to substantially eliminate the signal voltage therein without largely reducing the signal-interference voltage common to the two circuits; electron tube means comprising two anodes, and two control grids for respectively controlling electron flow to said anodes, said grids being respectively connected to said input circuits; resistance means including two substantially identical resistor sections providing two end terminals connected respectively to said anodes and interconnected for connection to a source of anode potential whereby substantially equal potentials are supplied to said anodes; a voltagedividing output resistor providing end terminals and providing a circuit-balancing adjustable output contact; and a pair of condensers respectively connecting said anodes to said end terminals of said voltage-dividing output resistor to insure the exclusive presence of alternating currents in said output resistor.

FRANK C. STREBE. WILLIAM L. COMYNS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,245,266 Pickard Nov. 6, 1917 1,309,400 Espenschied July 8, 1919 1,628,676 Meissner May 17, 1927 1,708,536 Esau Apr. 9, 1929 1,716,573 Armstrong June 11, 1929 1,692,877 Vreeland Nov. 27, 1928 1,733,414 Knapp Oct. 29, 1929 1,746,829 Goodrum Feb. 11, 1930 1,748,277 Chaffee Feb. 25, 1930 1,821,906 Cohen Sept. 1, 1931 2,000,142 Loweenstein May 7, 1935 2,031,607 Kane Feb. 25, 1936 2,227,415 Wolff Dec. 31, 1940 2,032,117 Corbett Feb. 25, 1936 1,476,691 Cohen et a1 Dec. 11, 1923 FOREIGN PATENTS Number Country Date 183,416 Great Britain Jan. 25, 1923 791,121 France Sept. 23, 1935 

